Document Type

Thesis - Open Access

Award Date

2024

Degree Name

Master of Science (MS)

Department / School

Veterinary and Biomedical Sciences

First Advisor

Sunil Mor

Abstract

Avian metapneumovirus (aMPV) is one the most economically important poultry respiratory pathogens belonging to the family Pneumoviridae and genus Metapneumovirus, which can affect both domestic and wild birds. aMPVs are classified into four subgroups (A, B, C, and D) based on the level of genetic variations and antigenic differences. aMPV causes turkey rhinotracheitis (TRT) and swollen head syndrome (SHS) in turkeys and chickens respectively. Recently, outbreaks of respiratory disease in meat-type birds and a significant decline in egg production with respiratory signs in breeders were reported from different states in the USA. Isolating aMPV is challenging as it is a fastidious organism. Furthermore, it is shed by the affected bird only during a short time window which is either before or just after the appearance of clinical signs. Additionally, there is no standardized cell line or method for its isolation. Thus, for increasing the probability of isolating aMPV, 22 real time RT-PCR confirmed positive samples were inoculated on four different cell lines (turkey tracheal cells, Vero E6, Qt-35, chicken embryo fibroblast) including in-house developed turkey tracheal (TT) primary cell line with different media composition. Cytopathic effects were observed on TT cells after performing five blind passages with the TCID50 of 105.5. The virus was adapted to continuous Vero E6 cells using several different compositions. Now aMPV is growing on Vero E6 cells with two different compositions with TCID50 of 106.5. In this thesis, I report a retrospective analysis of aMPV submissions to the ADRDLSDSU in the last eight months (January to August 2024) and confirm that submission of aMPV positive cases has indeed increased. During this period, 1487 samples from 863 farms were tested out of which 489 samples from 331 farms were found positive for either subgroup A or B. Majority of the positive samples were from birds < 10 weeks, and the most common samples type tested was choanal cleft swabs. Based on our datasets, majority of the positive samples were detected in winter and spring 2024. Within these eight months, 11 states have been found positive for either of the subgroups. Overall, my thesis will provide a framework for successful isolation and adaption of aMPV subgroup B and insights about the distribution of aMPV in USA along with effects of other factors like age, season, geographical distribution, and samples type.

Library of Congress Subject Headings

Poultry -- Virus diseases.
Poultry -- Virus diseases -- Epidemiology.
Virus diseases -- Molecular diagnosis.
Molecular epidemiology.

Publisher

South Dakota State University

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Rights Statement

In Copyright